This project is concerned primarily with the physiology of vertebrate photoreceptors, the processing of visual information within the retina, and the mechanisms underlying retinal responses. Both intra- and extracellular recordings will be made from photoreceptors and retinal neurons in selected species. Specific problems to be investigated include: 1) The ionic basis for, and the mechanisms of generation of, the slow sustained responses of the horizontal and bipolar cells in the goldfish and skate retinas. 2) The mechanisms involved in network adaptation and lateral adaptive effects occurring across the skate retina. 3) The physiology of the pineal eye in the lamprey. 4) The physiology of tectal cells in the lamprey.